Immunodeficiency in a Patient with 22q11.2 Distal Deletion Syndrome and a p.Ala7dup Variant in the MAPK1 Gene

The genetic basis for sporadic immunodeficiency in patients with 22q11.2 distal deletion syndrome is unknown. We report an adult with a type 1 (D-F) 22q11.2 distal deletion syndrome and recurrent severe infections due to herpes zoster virus, presenting mild T cell lymphopenia and diminished frequency of naive CD4⁺ T cells, but increased frequencies of central, effector, and terminally differentiated memory T cells. Antigen-specific CD4⁺ and CD8⁺ T cells to influenza, rotavirus, and SEB were conserved in the patient, but responses to tetanus toxoid were temporarily undetectable. Exomic sequencing identified the c.20-22dupCGG (NM-002745.4) variant in the remaining MAPK1 gene of the patient, which adds 1 alanine to the polyalanine amino-terminal tract of the protein (p.Ala7dup). The mother, unlike the father, was heterozygote for the variant. Western blot analysis with the patient's activated PBMCs showed a 91% reduction in the MAPK1 protein. Further studies will be necessary to determine whether or not the variant present in the remaining MAPK1 gene of the patient is pathogenic.